1971 9.5 Johnson, idle problem

When I set the idle on the 9.5 it seems to change on it's own?. I mean, I get it to idle nice and smooth in neutral, then put it into gear. From there it starts to stubble a little so I give it a hair more throttle the back off it again. It idle's faster for about 30sec then drops to where I want it, then starts to pickup on it's own again. I've tried adjusting the low speed mix, within that 1/4 turn someone had suggested. But I just can't get it to idle smoothly in gear without stubbling or idling to fast. Could this be a float level issue, and if so what should the float level be. <br /><br /> I realize this engine is no spring chicken, but I can't help but feel that it could idle smoother in gear.

Re: 1971 9.5 Johnson, idle problem

sounds like it might be sucking air from some where.or maybe a pluged jet in the carb. did you rebuild the carb yet?

Re: 1971 9.5 Johnson, idle problem

No I haven't put a kit in the carb Wayne. I gave it a good cleaning and inspection though. The needle valve and seat look good, with no wear ring on the needle. I've been having trouble with the coupler on the fuel line(tank end). I put a new OMC coupler on the hose but I'm still not happy with the fit . Could this be the source of my idle problem?. The coupler at the tank seem's to have sealed it self, but still stands off about a 1/16 of an inch after it's clicked in.

Re: 1971 9.5 Johnson, idle problem

Knot,<br /><br />Wide variations in the amount of fuel getting to your carb can give you erratic performance problems. When you mentioned "It idle's faster for about 30sec then drops to where I want it, then starts to pickup on it's own again" could mean the mixture is leaning out, and the rpm's will climb. When you say that you gave the carb a good cleaning, did you make sure the low idle circuit was cleaned and blown out with compressed air?? Remove the low speed idle screw and inspect it for a worn ring at the tip. Spray carb cleaner into the low speed idle screw hole and blow it out. Count the turns it takes to lightly close the valve, you can use this setting when you re-install the needle valve. You can go to initial needle settings too, lightly close needle valve then open 1 1/2 turns, this should get it started. Let it warm to operating temp and slowly close needle valve in 1/4 turn increments, waiting between adjustments for the motor to respond. At some point she'll stumble (too lean), then back out (open) 1/4 turn. Tweak the needle in or out just a little for best idle.<br /><br />A carb rebuild certainly couldn't hurt at this point if you have any doubts about the float needle valve and float level setting. Cleaning a carb is more about the insides being free of old gas deposits (varnish) and the passages being free and clear. Check to be sure your fuel hoses are air tight and not sucking air and that the tank is vented too. All these things you probably already know but are worth a second look.

Re: 1971 9.5 Johnson, idle problem

Thanx for the reply Xcusme. I did all the procedures you mentioned. I generally work on snowmobiles, so I know the importance of of cleaning the carb well and using compressed air to blow out the idle circuit etc. I did have a problem with the fitting on the gas tank and have fixed that now.<br /><br />I took the motor out, for it's maiden lake run yesterday and it ran beautiful! Never skipped a beat all day, and seems to have adequate power for my 12' alum. So I think the tank fitting, was source of the air leak. <br /><br />I live in the mountains, so alot of times you have to keep re-adjusting carbs. I mean, you barrel test at 1200ft and go boating at 4500ft.

Re: 1971 9.5 Johnson, idle problem

Knot,<br /><br />Hey, that's really good news! You are a testament to the fact that a little common sense, some perseverance, and a big hammer , can fix just about anything. Well done, glad you got it fixed.

Re: 1971 9.5 Johnson, idle problem

My wife always say's, I' m like a dog lookin' for his bone, when it comes to fixing things. Finding people with direct knowledge and a willingness to share that knowledge, has bin a real plus.<br /><br />I think I might even take another crack, at getting my 59' JW15 running smoothly!.<br /><br />Thanx again, Darrell

Re: 1971 9.5 Johnson, idle problem

WIND KNOT <br />how did the boat plane out ? reason why i ask id because i have a hell of a time getting mine on plane i am going to try a hydorfoil J.R. for small engines because i tryed everything else

Re: 1971 9.5 Johnson, idle problem

Wayne, it wasn't the greatest day for a test run(real choppy conditions). It felt like it was up a couple times, but only when I was going with the wind. The motor does seem to sit in the the water a little deep though. Did you try your transom spacer yet?. I was thinking of making a plate that would bolt to the original antivent plate too. Maybe a aluminum plate the same shape, only with a couple inches more diameter?.